function [head,tail] = get_section_zone(L,section_len,head) %L is beat_len set,always be M0(2), section_len is the section's beat_len
tail = head;
len = 0;  % temp of time length
while len<section_len && tail <= length(L)  
    len = len + L(tail);  % len add
    tail = tail+1;
end
tail = tail -1;
end

